1. Field of the Invention
The present invention relates to an image processing apparatus, and more particularly, to an image processing apparatus which has a copying function and embeds a tracking code in an output image.
2. Description of the Related Art
Color copying machines (hereinafter simply referred to as “copying machines”) are capable of embedding a tracking code known as a pattern code in the output image. The pattern code is generated as follows. A unique code assigned to each individual model of copying machine that outputs an image is converted into dot data in accordance with a certain encryption rule and an image hidden in the output image, a pattern code, is generated on the dot data. The pattern code is made up of fine, faint color dots generated using yellow toner and is hardly visible in an output image to the naked eye (see Japanese Laid-Open Patent Publication No. 2005-151456, for example).
A pattern code embedded in an output image can be read by using an image reader such as a scanner capable of reading pattern codes to track back to identify the model of copying machine that outputted the image.
However, with the conventional technique, only the model of copying machine that outputted an image can be identified by reading a pattern code embedded in the output image. It is impossible to identify with this technique which of the copying machines of the same model outputted the image. To make it possible to track each individual copying machine by reading a pattern code, every individual copying machine must have a unique pattern code. To generate such unique pattern codes, every individual copying machine must have a code associated with the machine and a memory adapted to store the code in it. In addition, the code and the pattern code must be managed in such a manner that they match each other. Generating a unique pattern code for every individual copying machine is not practical because of operational costs. Therefore, a given pattern code for copying machines of the same model is generated and embedded in output images to provide traceability. However, it is difficult to trace back to identify the copying machine that formed an output image among the machines of the same model using the pattern code of the model.
Furthermore, since pattern codes are generated from unique codes assigned to copying machines in accordance with a certain encryption rule, they can be forged by decrypting the unique codes and the encryption rule.